This invention relates to a novel cover for a wall box mounted switch, receptacle, display or other device of the type which employs an integral yoke plate having a shallow insulation escutcheon protruding from one surface thereof, which escutcheon can contain an operating member which is externally operable from a position in front of the wall box and more specifically relates to a novel two part cover plate.
Wall box mounted devices and switches are well known. The term "switch" as used herein is intended to encompass devices employing on/off contacts and/or dimming controls. The on/off contact may be employed as the sole control means of the switch and may be manually operable by a toggle. The device may also employ a dimmer control such as a rotary or longitudinally movable adjustment device which operates with or without an on/off switch. One known switch is sold by Lutron Electronics Co., Inc., the assignee of the present invention, under its trademark "SKYLARK".
One SKYLARK switch device employs a linearly movable control member which causes a dimming function and operates an on/off switch at the end of its longitudinal motion. In another SKYLARK switch model, the on/off switch is a toggle switch which operates independently of the slide dimmer control so that the switch can be turned on and off without changing the dimmer setting.
The dimmer slide of the SKYLARK switch devices is contained within an elongated rectangular escutcheon which extends from the front surface of the yoke plate. A conventional back box containing the switch mechanism extends from the rear surface of the yoke plate. A pair of flexible leads extend through the back box to be electrically connected to wiring contained within the wall box within which the device is mounted.
The switch referred to above is but one of a large number of known devices which contain a rectangular escutcheon extending from the front surface of the yoke plate. In some, the entire front of the escutcheon contains a single toggle switch operator or outlet socket. Devices of this class are identified by NEMA Standards Publication No. WD6-1983, page 6, which discloses the NEMA rectangular face device with an escutcheon projecting from the front of a yoke plate.
The yoke plate of such devices has a pair of laterally extended openings slightly removed from the top and bottom of the escutcheon, which openings receive standard mounting screws which are positioned to thread into threaded openings in a standard wall box. That is, the center-to-center spacing of the laterally extended openings in the yoke plate is the same as the center-to-center spacing of the screw receiving openings in a wall box.
A second pair of openings are disposed above and below the two mounting openings respectively. These latter two openings are threaded and are on a spacing equal to that of the openings in a wall plate which is adapted to cover the yoke plate and escutcheon of the device and to be held in place by screws. The spacing of these openings is standard so that any manufacturer's wall plate can be connected to and cover any manufacturer's device. The threaded openings are adapted to receive 6-32 screws on a standardized center-to-center distance of 3.812 inches.
The purpose of the wall plate is to provide a decorative cover for the front of the escutcheon and yoke plate, as well as to prevent access to the interior of the wall box which contains electrical wiring. Standard wall plates have central openings large enough to receive the device escutcheon. However, the screw heads which mount the cover plate to the device are visible at the cover plate surface, thus giving the surface a cluttered appearance. Furthermore, when the wall plate is removed, either intentionally or accidentally, it is possible frequently for a person to gain access to the interior of the wall box due to uncovered openings between the edges of the yoke plate and the sides of the wall box. This creates a dangerous situation, particularly to children who are unaware of the danger and may poke foreign objects into the wall box or even put their fingers into the wall box.
Custom face plates have been manufactured and are available for use with only one switch wherein the custom wall plate can be snapped onto its respective switch. Both the yoke plate for the switch and the cover must be made with surface snaps in cooperating locations. The custom wall plate cannot be used with any other switch. One device of this type is device model No. NK09051T, sold by National. This device does not have the standard escutcheon size set forth in the NEMA Standard Publication No. WD6-1983, page 6. Obviously, the wall plate supplied with the device is not interchangeable with other rectangular face devices. Moreover, if the wall plate is removed, interior wiring may be accessed, leading to potentially dangerous situations, particularly since the wall plate can be removed without special tools.
Another custom wall plate device is known, sold by National, under number NK09080. This device employs a two-piece face plate assembly for a switch of non-NEMA standard configuration. That is, this switch has a front escutcheon which is longer than the NEMA standard and has a width less than the NEMA standard value. The device has a wide frame plate which is intended to overlap the wall surrounding the wall opening for the wall box and defines an outer decorative finish. This frame is screwed into place in the screw hole openings in the device yoke plate which are intended to receive a decorative plate. However, a very large, central opening is formed in the frame so that a gap exists between the edges of the metal yoke plate and the interior of the frame opening. A narrow decorative plate is then snapped over the escutcheon and into snap receiving openings within the outer frame. Again, this decorative plate can be removed without use of special tools and, when removed, exposes a dangerous gap between the frame and the yoke plate of the switching device, which exposes the wiring within the wall box.
Decorative plates are also known for conventional toggle switches in which the operating handle protrudes through a relatively small rectangular opening. These switches do not employ an insulation escutcheon extending from the front of the yoke plate. These devices, which are sold by Edmar Creations Inc. of Clifton, N.J., employ a large area clear plastic frame which is screwed into a wall box and overlaps the wall opening. A decorative cover is then snapped into a recessed front surface of the clear plastic frame. The screws for mounting the device to the wall box are on centers inappropriate for the mounting of a switch of the type having a NEMA extending escutcheon, and the opening of these devices cannot receive the escutcheon of such a device. Moreover, the device presents a relatively wide plastic frame enclosing the wall box opening.
Another prior art structure is that of U.S. Pat. No. 2,740,873 in the name of K. P. Cronk. The device shown in that patent employs a custom snap-in plate which is adapted to snap into a specially prepared yoke plate for the switch mechanism. The yoke plate is a custom yoke plate which is adapted to mount and carry the switch mechanism and to connect the switch mechanism to the wall box. Consequently, the decorative plate of Cronk fits only the customized yoke plate and cannot be used for other switch structures.